1. Field of the Invention
The invention relates to a method for improving manufacturing accuracy of a spindle motor and, more particularly, to a method for improving altitude and run-out of a slim-type spindle motor.
2. Description of the Related Art
Prosperity in information development has propelled the significance of developing information storage medium. Regarding to information storage medium, a spindle motor has been playing a major role in the field. A spindle motor is a small motor, which mostly functions as a driving device for activating operation of information storage medium such as compact disk drive and hard disk drive. The types of spindle motor may vary, but the primary components of all types of spindle motor are the same, including a loading surface, a rotating shaft, a rotor, and a stator. Among them, a loading surface can be the surface of a loading disk that is independently provided or the surface of a motor rotor itself, and both of them can be used for loading or activating a hard disk or compact disk. On the other hand, manufacturing for spindle motors has been turned to miniaturization actuated by the more precise modern manufacturing techniques. For instance, FIGS. 1 & 2 represent a perspective diagram and a sectional diagram along the line A—A of FIG. 1 respectively according to a conventional slim-type spindle motor.
As shown in FIGS. 1 & 2, a slim-type spindle motor is composed of several parts of components. Also, because the spindle motor's volume is small and its running speed can reach thousands of rotations per minute (rpm), normally there will be some requirements made to raise processing accuracy for each component of the spindle motor so that big vibrations can be avoided when the disk is in operation. Through the requirements, data reading on the disk will not be affected, nor will the optical read head be damaged. However, doing so can also increase the manufacturing cost. Besides, since a spindle motor comprises several parts of components, it is inevitable to accumulate assembly errors while assembling components for each part. Unfortunately, these accumulated errors can seriously decrease the stability of overall spindle motor operation.
To illustrate the above-mentioned drawback, the spindle motor 10 shown in FIG. 1 will be taken as an example. As shown in FIG. 1, the loading surface 11 is a surface of motor rotor 13, and an anti-sliding slice 14 is adhered to the motor rotor 13 thereon to prevent the disk from sliding. Besides, there are other components of spindle motor 10, including a shaft 12, a cap 15, a base 16, a driving circuit 17, a stator base 18 (shown in FIG. 2), windings 19 (shown in FIG. 2), and a permanent magnet 20 (shown in FIG. 2). After the assembly has been done, the vertical errors between the loading surface 11 of the slim-type spindle motor 10 and the shaft 12, the manufacturing errors residing in the spindle motor 10 itself, and the existing assembly errors are all possible to cause a run-out when the spindle motor 10 is running; that is, when rotating, the loading surface 11 can result in a run-out corresponding to the shaft 12. In other words, the aforementioned errors can lower the product yield.
On the other hand, concerning about the applicability of a conventional slim-type spindle motor, a designer of the spindle motor has to diminish the volume of the motor. Therefore, besides that the altitude of the spindle motor being placed inside the disk drive has to be diminished, the altitude also has to be precisely controlled so that the relative positions among the spindle motor, the disk, and the read head can be fixed to facilitate a precise read head's reading data from the disk. In brief, the altitude accuracy of a slim-type spindle motor being placed inside the disk drive is essential.
However, there is usually no need to install any independent loading disk for the case of the slim-type spindle motor. Instead, the surface of the motor rotor will be used directly as a loading surface. Under such circumstances, it will be labor consuming and time consuming to try to solve the aforementioned run-out problem of the loading surface and try to precisely control the altitude accuracy of the spindle motor. Therefore, it is the subject for us to look for an easy and accessible method to improve altitude accuracy of the spindle motor as well as to reduce run-out of a loading surface in a short time.